Measurement of the difference in flexoelectric coefficients of nematic liquid crystals using a twisted nematic geometry

Abstract

A technique for measuring the difference between the splay and bend flexoelectric coefficients in a nematic liquid crystal is demonstrated. The method uses the flexoelectric-optic effect, but instead of a uniform lying helix structure, a TN cell geometry with an in-plane electric field is used. This has the advantage of avoiding difficulties associated with aligning the helix and can be used to measure achiral materials. The effects due to ionic screening are also taken into account.

Mechanisms of flexoelectric switching in a zenithally bistable nematic device

“…In either case, the magnitude of the relevant coefficient ͑sum or dif-ference͒ is of the same order of magnitude as those measured in E7. 28,29 …”

P-131: Studies on Flickering in Low Frequency Driven Fringe-Field Switching (FFS) Liquid Crystal Display

“…The FFE is a phenomenon that the distortion of the LC director and the electric polarization are coupled so that the polar axis of nematic LC is accompanied with splay and/or bend deformations. The polarization induced by FFE is given , , where is the unit vector of the LC orientation, e 11 and e 33 are splay and bend flexoelectric coefficients, respectively [9][10][11][12]. Under an applied electric field to the FFS mode, the electrode structure causes strong fringe electric fields and thus the field induces splay and bend deformations as schematically shown in Fig.…”

23-1:Distinguished Student Paper: Flexoelectric Effect on Image Flickering of Fringe Field Switching LCDs

“…(1), e 11 and e 33 are the two dominant factors governing the splay and bend deformations. Some methods for measuring e 11 and e 33 have been developed, although they are not simple [6][7][8][9]. In general, FEE is strong in a system whose molecules possess a large shape polarity as well as a large permanent dipole moment, which means there is a correlation between flexoelectric coefficients and dielectric anisotropy [4,6].…”